How to prevent a sentence beginning with the word "The"? [closed]

Solution 1:

Perhaps use the indefinite article "a" sometimes instead? Or refer to things in general (or plural) or as mass nouns, so you avoid articles (see the first point here, and see this guide to how you can use nouns without articles).

The main purpose of the presented applications is to visualize roses in space. A user can run around and experience the roses from different angles.

And clauses to promote flow without always referring to a subject immediately:

The main purpose of the presented applications is to visualize roses in space. By running around, a user can experience roses from different angles. Positions of the roses can be stored in ROS-file formats.

Solution 2:

Pluralize, with discretion.

The main purpose of the presented applications is to visualize roses in space. Users can run around and experience the roses from different angles. Positions of the roses can be stored in the ROS-fileformat.